creat(2) manual page
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creat - create a new file or rewrite an existing one
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
int creat(const char *path, mode_t mode);
Async-Signal-Safe
creat() creates a new ordinary file or prepares to rewrite an existing
file named by the path name pointed to by path.
If the file exists, the
length is truncated to 0 and the mode and owner are unchanged.
If the file
does not exist the file’s owner ID
is set to the effective user ID
of the
process. The group ID
of the file is set to the effective group ID
of the
process, or if the S_ISGID bit is set in the parent directory then the
group ID
of the file is inherited from the parent directory. The access
permission bits of the file mode are set to the value of mode modified
as follows:
- If the group ID
of the new file does not match the effective
group ID
or one of the supplementary group ID
s, the S_ISGID bit is cleared.
- All bits set in the process’s file mode creation mask are cleared (see
umask(2)
).
- The ‘save text image after execution bit’ of the mode is cleared
(see chmod(2)
for the values of mode).
Upon successful completion, a write-only
file descriptor is returned and the file is open for writing, even if the
mode does not permit writing. The file pointer is set to the beginning of
the file. The file descriptor is set to remain open across exec functions
(see fcntl(2)
). A new file may be created with a mode that forbids writing.
The call creat(path, mode) is equivalent to:
open(path, O_WRONLY | O_CREAT
| O_TRUNC, mode)
Upon successful completion a non-negative integer, namely
the lowest numbered unused file descriptor, is returned. Otherwise, a value
of -1 is returned, no files are created or modified, and errno is set to
indicate the error.
creat() fails if one or more of the following
are true:
- EACCES
- Search permission is denied on a component of the path
prefix.
- The file does not exist and the directory in which the file
- is to
be created does not permit writing.
- The file exists and write permission
is denied.
-
- EAGAIN
- The file exists, mandatory file/record locking is set,
and there are outstanding record locks on the file (see chmod(2)
).
- EDQUOT
- The directory where the new file entry is being placed cannot be extended
because the user’s quota of disk blocks on that file system has been exhausted.
- The user’s quota of inodes on the file system where
- the file is being created
has been exhausted.
- EFAULT
- path points to an illegal address.
- EINTR
- A signal
was caught during the creat() function.
- EISDIR
- The named file is an existing
directory.
- ELOOP
- Too many symbolic links were encountered in translating
path.
- EMFILE
- The process has too many open files (see getrlimit(2)
).
- EMULTIHOP
- Components of path require hopping to multiple remote machines.
- ENAMETOOLONG
- The length of the path argument exceeds {PATH_MAX}, or the length of a
path component exceeds {NAME_MAX} while {_POSIX_NO_TRUNC} is in effect.
- ENFILE
- The system file table is full.
- ENOENT
- A component of the path prefix
does not exist.
- The path name is null.
-
- ENOLINK
- path points to a remote machine
and the link to that machine is no longer active.
- ENOSPC
- The file system
is out of inodes.
- ENOTDIR
- A component of the path prefix is not a directory.
- EROFS
- The named file resides or would reside on a read-only file system.
chmod(2)
, close(2)
, dup(2)
, fcntl(2)
, getrlimit(2)
, lseek(2)
, open(2)
,
read(2)
, umask(2)
, write(2)
, stat(5)
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